A typical microorganism lipid manufacturing process, such as production of omega-3 highly unsaturated fatty acid, in particular docosahexaenoic acid (DHA), involves growing microorganisms which are capable of producing the desired lipid in a fermentor, pond or bioreactor, isolating the microbial biomass, drying it, and extracting intracellular lipids with an organic solvent, e.g., hexane. Generally, intracellular lipids of microorganisms are extracted after rupturing (i.e., lysing) the cells of the microorganisms. The extracted lipids are can be further refined to produce a high purity and/or quality lipids. The microorganisms are generally isolated by first diluting the fermentation broth with water, and centrifuging the mixture to isolate microorganisms. When lipids are not extracted immediately or soon after isolating the microorganisms, the isolated microorganisms are typically dried, for example, on a drum dryer, and packaged, for example, in vacuum-sealed bags, to prevent degradation of lipids.
Unfortunately, the drying process exposes the microorganisms to heat, which can damage, i.e., degrade the quality of, lipids if done incorrectly. The vacuum-sealed bags may develop leaks, which can further degrade the quality of the lipids due to exposure of the microorganisms to air. In addition, if the dried microorganisms are not treated with an antioxidant, lipids can be further degraded due to exposure to air, for example, DHA may degrade due to oxidation by air. Furthermore, in some cases operators who are exposed to the dried microorganisms can develop an allergic reaction creating a safety and/or health hazard to operators.
Moreover, in an industrial scale production, the amount of organic solvent used in lipid extraction typically requires a large amount of volatile and flammable organic solvent, thereby creating hazardous operating conditions. The use of organic solvent in the extraction process may necessitate using an explosion-proof oil recovery system, thereby adding to the cost of lipid recovery. Moreover, use of an organic solvent in extracting lipids from microorganisms generate an organic solvent waste stream requiring a proper method, which further increases the overall production cost of lipid extraction.
Therefore, there is a need for a process for extracting lipids from microorganisms which does not require the use of an organic solvent. There is also a need for a lipid extraction process from microorganisms which does not require the expensive step of drying the microorganisms.